Acoustic analysis of a state of a machine

ABSTRACT

In order to provide an acoustic analysis of a condition of a machine ( 8 ) having reduced computational complexity, a method for generating at least one reference signal ( 20 ) is provided. An individual acoustic signal is provided for each of at least two components ( 14, 15, 16 ) of the machine ( 8 ). A total acoustic signal which is to be expected is determined on the basis of the individual signals by means of a computing unit ( 13 ). The reference signal ( 20 ) is generated by means of the computing unit ( 13 ) in accordance with the total signal.

The present invention relates to a method for generating at least one reference signal for the acoustic analysis of a state of a machine, to a method for the acoustic analysis of a state of a machine, wherein an acoustic operating signal is recorded during operation of the machine, to a corresponding analysis apparatus and to a computer program and a computer-readable storage medium.

Data analysis methods are becoming more widespread in industrial manufacturing, for example, which data analysis methods are aimed, inter alia, at predictive planning of maintenance work on machines in order to thus be able to minimize downtimes or losses in quality in the manufacturing process (“predictive maintenance”).

In known methods, state data relating to a machine which are captured during the process are analyzed on the basis of machine learning methods, and an attempt is made to derive significant trends. Large volumes of data are possibly required for this purpose in order to be able to make reliable predictions, and accordingly high computing capacities are thus required.

Further disadvantages of known methods are their sometimes large outlay on instrumentation, a restricted field of application or a lack of automation capability.

Against this background, an object of the present invention is to specify an improved concept for the acoustic analysis of a state of a machine, which can be taken as a basis for reducing a volume of data to be processed and computing effort required for processing.

According to the invention, this object is achieved in each case by means of the subject matter of the independent claims. The dependent claims relate to advantageous developments and configurations.

The improved concept is based on the idea of providing acoustic individual signals for individual components of the machine and generating a reference signal on the basis thereof.

A first independent aspect of the improved concept specifies a method for generating at least one reference signal for the acoustic analysis of a state of a machine. In this case, at least one acoustic individual signal is provided for each of at least two components of the machine. An expected acoustic overall signal is determined on the basis of the individual signals by means of a computing unit. The reference signal is generated on the basis of the overall signal by means of the computing unit.

The acoustic analysis of the machine can be understood as meaning, in particular, an analysis of an operating noise of the machine. In particular, the acoustic analysis comprises the analysis of airborne sound waves which are generated by operation of the machine.

The computing unit may comprise one or more subunits or processor units which may be arranged in a spatially distributed manner, for example. In particular, different method steps can be carried out by different subunits of the computing unit.

A component of the machine is, in particular, a noise-emitting component of the machine. The component may have, for example, a motor, a gear apparatus and/or other electrical elements or mechanically movable parts.

The provision of the acoustic individual signals comprises, in particular, the generation of the respective acoustic individual signals. In this case, the individual signals can be generated by capturing respective individual operating noises of the corresponding components by means of a sound transducer. Alternatively, complementarily or additionally, the generation of the individual signals may comprise a simulation, that is to say synthetic generation as it were, of the acoustic individual signals.

Here and below, a sound transducer may be understood as meaning a sound sensor or a sound receiver, that is to say a sensor or receiving unit which is configured to convert airborne sound into electrical signals. In particular, a sound transducer may be in the form of a microphone.

The sound transducer and the computing unit may be part of an analysis apparatus for the acoustic analysis of a state of a machine, for example.

According to at least one embodiment, the at least one associated acoustic individual signal is generated for each of the at least two components of the machine on the basis of respective individual operating noises of the corresponding component, in particular by means of a sound transducer.

In this case, the acoustic individual signals are generated, in particular, on the basis of the individual operating noises of the respective components in a reference or new state of the machine.

In particular, an associated acoustic individual signal is provided or generated for each component of the machine and for each individual operating state of the component, wherein each individual operating state of a component is selected from a predefined set of individual operating states of the component.

The acoustic individual signals for a given component of the at least two components are, in particular, independent of further components of the at least two components. This means that further components of the at least two components do not contribute to the respective individual operating noise of the given component. In other words, the individual operating noises of the individual components are individually captured, in particular while the further components of the at least two components are not operating or are acoustically isolated from the given component.

Here and below, the recording or pick-up of a noise, particular an operating or individual operating noise, may be understood as meaning the capture of the respective operating noise, in particular by means of at least one sound transducer, and the subsequent storage of the signal generated thereby on a computer-readable storage medium, for example of the computing unit.

The individual signals may be provided, in particular, as time-dependent signals or as signals in a frequency domain. Accordingly, the overall signal and/or the reference signal may each be generated as a time-dependent signal or as a signal in the frequency domain.

As a result of the fact that one or more individual associated acoustic individual signals are generated or provided for each of the at least two components and are taken as a basis for generating the overall signal and the reference signal, the individual components of the machine are individually taken into account independently of one another in order to generate the reference signal. As a result, it is possible to specifically take into account additional influences which contribute to the overall signal or the reference signal, for example environmental or interfering influences, for example on the basis of empirical data, simulation data or on the basis of theoretical or partially theoretical models.

As a result of the fact that the acoustic individual signals, which can be understood as meaning, for example, nominal signals or nominal noises of the individual components in the reference or new state of the machine, are known, it is only necessary, during the subsequent analysis of the state of the machine with reference to the reference signal, to capture an overall operating noise of the overall machine. In particular, it is not necessary to also include the individual operating noises of the individual components during the analysis of the state of the machine since the influences of the individual components can be separated or isolated from the overall noise or overall operating noise of the machine. Accordingly, it is possible to record the operating noise in a manner relatively far away from the component for the purpose of analyzing the state of the machine and recording of the noise close to the component is not necessary.

In comparison with other acoustic analysis methods, this results in the advantage that, according to the improved concept, a lower outlay on instrumentation is required, in particular as far as the number and positioning of one or more sound transducers are concerned. In particular, according to the improved concept, one sound transducer may suffice to record the operating noise of the machine for analyzing the state.

According to at least one embodiment, a respective first individual signal is recorded for each of the at least two components while the respective component is in the corresponding first individual operating state. The overall signal is determined on the basis of the first individual signals by means of the computing unit. In this case, a combination, in particular a predefined combination, of the first individual operating states of the at least two components, in particular of all of the at least two components, defines a first operating state of the machine.

In other words, a first individual state is defined for each of the at least two components. The combination of all first individual states defines or forms the first operating state of the machine. In particular, each possible operating state of the machine may be defined as a predefined combination of corresponding individual operating states of the at least two components of the machine.

An individual operating state of one of the at least two components may comprise, for example, one or more predefined operating parameters for the component and/or one or more environmental parameters for the component. Depending on the type of machine and component, the operating parameters may comprise, for example, a speed, a gear ratio, a feed speed, a load or the like. The environmental parameters of the component may be, for example, a temperature or another environmental condition in an environment of the component.

The overall signal is determined, for example, on the basis of the first individual signals by using those signals of the first individual signals which correspond to the corresponding individual operating states of the components, which together make up the first operating state of the machine, to generate the overall signal.

A model for generating the overall signal can be improved by adapting or varying the individual operating states or the operating state of the machine. This improves the accuracy of the reference signal and therefore the analysis of the state of the machine.

According to at least one embodiment, a second operating state of the machine is given by a defined combination of respective second individual operating states of the at least two components. A respective second individual signal is recorded for each of the at least two components while the respective component is in the corresponding second individual operating state. The overall signal is determined on the basis of the second individual signals.

In particular, the second operating state of the machine differs from the first operating state of the machine. Accordingly, at least one of the second individual operating states of the at least two components differs from the corresponding first individual operating state of the respective component. It is possible, but not absolutely necessary, for all first individual operating states to differ from the corresponding second individual operating states.

According to at least one embodiment, the reference signal is the same as the overall signal.

According to at least one embodiment, the reference signal is generated, as described above, by determining a plurality of overall signals for different operating states of the machine and generating the reference signal on the basis of the plurality of overall signals, for example by means of interpolation.

As a result, it is not necessary to determine a separate acoustic overall signal for each relevant operating state of the machine, which is possibly intended to be acoustically analyzed, by combining separately recorded individual signals. Rather, it suffices to select representative operating states of the machine as supporting points as it were and to generate the overall signal for them, as described. The reference signal for a representative operating state then corresponds to the respective overall signal, whereas the reference signal for an operating state not belonging to the representative operating states is generated on the basis of overall signals of two or more representative operating states, for example by means of interpolation or combination.

According to at least one embodiment, the overall signal is generated on the basis of the individual signals using a model.

In the simplest case, the model may involve adding the separate individual signals or adding them in a weighted manner, wherein the model comprises the corresponding weighting factors. In more complex embodiments, the model may take into account, in addition to the individual signals, further influences, for example interfering noises or other interference, a geometrical structure of the machine, environmental conditions of the machine and/or material-specific noise signatures of the machine, in order to generate the overall signal.

According to at least one embodiment, the acoustic overall signal is determined on the basis of a pose of one of the at least two components or on the basis of two or more poses of two or more of the at least two components by means of the computing unit.

Here and below, the pose of a component may be understood as meaning a combination of the position and orientation of the respective component in three-dimensional space. In this case, the position and orientation of the component may be defined with respect to one or more further components of the at least two components, with respect to a further component part of the machine or with respect to an object in the environment of the machine, for example a building floor, a building wall or a further machine.

The pose of the components may influence how the individual signals are to be weighted in order to form the expected overall signal. In addition, the influence of external influences may also depend on the poses. Taking the pose into account therefore achieves improved accuracy of the reference signal and ultimately of the analysis of the state of the machine.

According to at least one embodiment, the pose of one of the at least two components or the poses of all of the at least two components is/are stored on a storage medium, for example of the computing unit. The computing unit can access the stored pose(s) in order to generate the overall signal.

According to at least one embodiment, the acoustic overall signal is determined on the basis of a nominal environmental condition of the machine by means of the computing unit.

The nominal environmental condition is not, in particular, a measured value, but rather one or more model parameters for generating or determining the overall signal from the individual signals. Depending on the environmental condition, different individual signals can be reflected differently in the overall signal, for example, and/or the external influences on the overall signal may depend on the environmental condition.

The nominal environmental condition may be, for example, a temperature or humidity in the environment of the machine, a background or interfering noise, a size or nature of a room in which the machine is arranged and/or the type and positioning or orientation of further objects or machines in the room.

The accuracy when generating the overall signal can be improved by virtue of the fact that the model for determining the overall signal takes into account the nominal environmental condition.

According to at least one embodiment, a current environmental condition of the machine is determined, in particular measured, by means of a sensor apparatus, in particular of the analysis apparatus. The reference signal is determined on the basis of the current environmental condition, in particular on the basis of a difference value between the current environmental condition and the nominal environmental condition, by means of the computing unit.

The determination of the overall signal can be improved further by taking into account the actual environmental condition or the deviation of the actual environmental condition from the nominal environmental condition.

A further independent aspect of the improved concept specifies a method for the acoustic analysis of a state of a machine, wherein an acoustic operating signal is recorded, in particular on the basis of a current operating noise of the machine, during operation of the machine, in particular by means of at least one sound transducer. A reference signal is provided on the basis of a method for generating at least one reference signal for the acoustic analysis of a state of a machine according to the improved concept. The state of the machine is analyzed on the basis of a deviation of the operating signal from the reference signal.

The reference signal is provided, in particular, by generating it by means of a method for generating a reference signal according to the improved concept.

As stated above, a single sound transducer or a few sound transducers may suffice to record the operating signal and a component-specific analysis of the state of the machine can nevertheless be carried out.

In comparison with analysis methods based on structure-borne sound measurements or thermographic measurements as well, outlay on instrumentation is reduced in a method according to the improved concept.

The state can also be analyzed in an automated manner by means of the improved concept since no manual investigations are necessary, for example investigations of wear debris in the machine oil, as is the case in ferrographic methods.

A further advantage of the improved concept is the universal applicability of the methods to virtually any desired machines having noise-emitting components.

As a result of the analysis according to the improved concept, in particular on the basis of a reference signal which was generated according to the improved concept, the volume of data which must be examined for analysis is relatively low. Therefore, it is possible to dispense with complex data analysis methods, as are used in deep learning or machine learning, for example. This also results in a reduced computing effort for the analysis. Accordingly, it is not necessary, in particular, to process the data to be analyzed in central backend or cloud servers. Rather, the analysis can be carried out in situ (“on premises”).

According to at least one embodiment of the method for the acoustic analysis of a state of a machine according to the improved concept, a current operating state of the machine is determined by means of the computing unit. The reference signal is provided on the basis of the current operating state by means of the computing unit.

In order to determine the current operating state, current operating parameters, for example, can be read from a control unit of the machine, in particular from a control program for controlling the machine, by means of the computing unit. For this purpose, the computing unit may be coupled to the control unit of the machine, in particular.

The current operating state of the machine is determined, for example, deterministically by the control program for the machine, in particular at any time. This makes it possible to predict the expected nominal acoustic behavior of the machine by appropriately providing the reference signal in a very limited timeframe.

In order to provide the reference signal on the basis of the current operating state, an overall signal generated for a representative operating state can be selected as the reference signal or the reference signal is generated on the basis of overall signals of two or more representative operating states, as stated above. In this case, after determining the current operating state, the respective overall signals can be generated on the basis of the model or may have already been generated and held in advance.

According to at least one embodiment, a difference signal is generated on the basis of the deviation of the operating signal from the reference signal by means of the computing unit. The state is analyzed on the basis of the difference signal by means of the computing unit.

This makes it possible to reduce the influence of noise as well as the evaluation complexity.

According to at least one embodiment, a frequency signal is generated on the basis of the difference signal by means of the computing unit. The state is analyzed on the basis of the frequency signal by means of the computing unit.

In order to generate the frequency signal, the difference signal, in particular, is subjected to a Fourier transform.

In such embodiments, the difference signal and, in particular, the reference signal and the operating signal are in the form of time-dependent signals.

Noise components can be hidden or removed, for example, in the frequency domain. This makes it possible to more clearly identify anomalous signal signatures or signal signatures which trace back to wear of the installation.

According to at least one embodiment, a check is carried out in order to determine whether there is an anomaly in the operation of the machine on the basis of the analysis of the state by means of the computing unit.

The anomaly is, in particular, a deviation of the current operating state of the machine or of current individual operating states of the components from expected states. The anomaly can trace back to a fault or defect, for example.

According to at least one embodiment, the computing unit is used to identify, on the basis of the analysis, which of the at least two components exhibits the anomaly.

This is possible, in particular, on account of the possible separation of the individual noise signatures of the components.

According to at least one embodiment, a degree of wear of the machine is determined on the basis of the analysis of the state by means of the computing unit.

According to at least one embodiment, an individual degree of wear of one or more of the at least two components is determined on the basis of the analysis of the state by means of the computing unit.

In particular, it is possible to distinguish between a possible anomaly and wear phenomena on the basis of characteristic signatures in the difference signal or in the frequency signal.

Further embodiments of the method for generating a reference signal according to the improved concept emerge directly from the different configurations of the method for analyzing a state of a machine according to the improved concept and vice versa.

A further independent aspect of the improved concept specifies an analysis apparatus for the acoustic analysis of a state of a machine, wherein the analysis apparatus has at least one sound transducer and a computing unit. The at least one sound transducer is configured to generate respective acoustic individual signals on the basis of respective individual operating noises of at least two components of the machine. The computing unit is configured to determine an expected acoustic overall signal on the basis of the individual signals. The computing unit is configured to generate a reference signal on the basis of the overall signal.

For example, the at least one sound transducer may comprise exactly one sound transducer. In such embodiments, the sound transducer may be positioned, for example, at different locations in order to record the respective individual operating noises and/or the sound transducer may be used to record the respective operating noises of the different components in succession.

Alternatively, the at least one sound transducer may comprise two or more sound transducers, wherein one or more of the sound transducers are used to record each of the individual operating noises.

The acoustic individual signals are stored, in particular, on a storage medium, in particular by means of the computing unit.

In other words, at least two acoustic individual signals are generated, wherein each of the at least two acoustic individual signals belongs to an associated component of the at least two components.

According to at least one embodiment, the analysis apparatus has a sensor apparatus which is configured to determine a current environmental condition of the machine. The computing unit is configured to determine the overall signal on the basis of the current environmental condition.

According to at least one embodiment, the at least one sound transducer is configured to generate an acoustic operating signal on the basis of an operating noise of the machine. The computing unit is configured to analyze the state on the basis of a deviation of the operating signal from the reference signal.

The operating noise of the machine is, in particular, an overall operating noise of the machine, that is to say an operating noise which is generated by a plurality of the at least two components together.

Further embodiments of the analysis apparatus emerge directly from the described configurations of the different methods according to the improved concept and vice versa in each case. In particular, an analysis apparatus according to the improved concept may be configured or programmed to carry out a method according to the improved concept, or the analysis apparatus carries out a method according to the improved concept.

A further independent aspect of the improved concept specifies a computer program having instructions. If the computer program is executed by a computer system, in particular by an analysis apparatus according to the improved concept, for example a computing unit of the analysis apparatus, the instructions cause the computer system, in particular the analysis apparatus, for example the computing unit, to carry out a method for generating at least one reference signal for the acoustic analysis of a state of a machine according to the improved concept.

A further independent aspect of the improved concept specifies a further computer program having further instructions. If the further computer program is executed by an analysis apparatus according to the improved concept, in particular by a computing unit of the analysis apparatus, the further instructions cause the analysis apparatus, in particular the computing unit, to carry out a method for the acoustic analysis of a state of a machine according to the improved concept.

A further independent aspect of the improved concept specifies a computer-readable storage medium on which a computer program and/or a further computer program according to the improved concept is/are stored.

The features and combinations of features mentioned in the description above and the features and combinations of features mentioned in the description of the figures below and/or shown in the figures alone can be used not only in the respectively stated combination, but also in other combinations, without departing from the scope of the invention. Embodiments and combinations of features which do not have all of the features of an originally formulated independent claim and/or go beyond or differ from the combinations of features stated in the dependency references of the claims can also be considered to have been disclosed.

The invention is explained in more detail below on the basis of specific exemplary embodiments and associated schematic drawings. In the figures, identical or functionally identical elements can be provided with the same reference signs. The description of identical or functionally identical elements is possibly not necessarily repeated with regard to different figures.

In the figures:

FIG. 1 shows a schematic illustration of an exemplary embodiment of an analysis apparatus according to the improved concept;

FIG. 2 shows a flowchart of an exemplary embodiment of a method according to the improved concept, in particular of a method for analyzing a state of a machine according to the improved concept; and

FIG. 3 shows signals in the context of a method according to FIG. 2.

FIG. 1 illustrates a machine 8 which may be in the form of an industrial robot or a machine for the subtractive or additive manufacturing of component parts, for example.

The machine 8 has, for example, a plurality of components, three components 14, 15, 16 in the schematic example in FIG. 1. The components 14, 15, 16 may have, for example, one or more corresponding motors or other noise-emitting component parts. In this case, a noise-emitting component part is referred to as such, for example, when it produces noises during operation of the machine 8, in particular a specific operating state of the machine 8.

The machine 8 also has a control unit 18 which is coupled to at least one of the components 14, 15, 16 in order to control it, inter alia.

FIG. 1 also shows a schematic illustration of an exemplary embodiment of an analysis apparatus 9 for the acoustic analysis of a state of the machine 8.

The analysis apparatus 9 has a computing unit 13 which is in the form of a computer system having one or more processor units, for example. The computing unit 13 is coupled to the control unit 18, for example. The analysis apparatus 9 also has at least one sound transducer, for example three microphones 10, 11, 12 in the non-restrictive example in FIG. 1. A first microphone 10 may be arranged in this case in an environment of a first component 14, a second microphone 11 may be arranged, for example, in an environment of a second component 15 and a third microphone 12 may be arranged, for example, in an environment of a third component 16.

The described arrangement of the microphones 10, 11, 12 may be provided, for example, for the purpose of carrying out a method for generating at least one reference signal according to the improved concept, as shown. In particular, the described arrangement of the microphones 10, 11, 12 may serve to record respective acoustic individual signals of the components 14, 15, 16 in order to generate the reference signal.

After the acoustic individual signals have been recorded, one or more or all of the microphones 10, 11, 12 may be arranged differently, in particular in order to record an operating noise of the machine 8, in particular an overall operating noise of the machine 8, in further steps of a method for the acoustic analysis according to the improved concept. All microphones 10, 11, 12 can be used for this purpose in different embodiments. In alternative embodiments, not all microphones 10, 11, 12 are used; for example, only one of the microphones 10, 11, 12 is used to record the operating noise of the machine 8.

The analysis apparatus 9 optionally has a sensor apparatus 17 which is connected or coupled to the computing unit 13, in particular in order to determine a current environmental condition, for example an ambient temperature, of the machine 8.

The computing unit 13 optionally has a computer-readable storage medium 19, in particular according to the improved concept, or the computing unit 13 is coupled to such a computer-readable storage medium 19.

The computing unit 13 may execute, for example, a computer program according to the improved concept which is stored on the computer-readable storage medium 19 in order to cause the analysis apparatus 9 to carry out a method according to the improved concept.

The method of operation of the analysis apparatus 9 in FIG. 1 is explained below with reference to an exemplary embodiment of a method for the acoustic analysis of a state of a machine according to the improved concept, in particular with reference to FIG. 2 and FIG. 3. The described method steps 1-7 need not necessarily be carried out in this case in the order suggested by their numbering.

FIG. 2 shows a flowchart of an exemplary embodiment of a method for the acoustic analysis of a state of the machine 8 according to the improved concept.

In step 1 of the method, the acoustic individual signals of the individual components 14, 15, 16 are recorded by means of the corresponding microphones 10, 11, 12, for example. In this case, a respective individual signal of a particular component 14, 15, is recorded in isolation from the other components, in particular. If the individual signal for the first component 14 is recorded, for example, any operating noise of further components 15, 16 is shielded from the first microphone 10. If possible, individual components of the other components 15, 16 can also be deactivated while recording the individual signal of the first component 14. The individual signals are generated, for example, for different individual operating states of the components 14, 15, 16.

As an alternative to using dedicated microphones 10, 11, 12 for each of the components 14, 15, 16, the individual signals of all components 14, 15, 16 can also be recorded using fewer microphones, for example using only one microphone, for example in succession.

In optional step 2 of the method, environmental conditions of the machine 8 are captured, for example, using the sensor apparatus 17. Alternatively or additionally, information relating to an arrangement and/or orientation, that is to say position and/or orientation, of the components 14, 15, 16, for example with respect to one another, can be loaded in optional step 2 by means of the computing unit 13, for example from the storage medium 19 or from the control unit 18.

In step 3 of the method, a current operating state of the machine 8 is determined. For this purpose, the computing unit 13 may access, for example, the control unit 18, for example a control program which is executed by means of the control unit 18, in order to determine current operating parameters or state parameters of the machine 8.

In step 4, the information from steps 1 and 3 and optionally from step 2 is processed in order to provide a reference signal.

In particular, the computing unit 13 determines, on the basis of the current operating state of the machine 8, which of the individual signals are combined with one another and how and are possibly combined with further information, for example the information from step 2 or other interfering influences or environmental influences, in order to generate the reference signal. Alternatively, various reference signals may also be generated in advance and the computing unit 13 selects one of them on the basis of the current operating state.

In step 5 of the method, an operating noise is captured during the current operating state of the machine 8 and is recorded as an operating signal by at least one of the microphones 10, 11, 12 or by means of a further microphone (not shown).

In step 6 of the method, the computing unit 13 generates a difference signal 22, for example on the basis of a deviation of the operating signal 21 from the reference signal.

The difference signal 22 may likewise be converted into a frequency signal, for example, in step 6, in particular by means of a Fourier transform of the difference signal 22.

In step 7, the computing unit 13 may analyze the difference signal 22 or the frequency signal, for example, in order to analyze the state of the machine 8.

For example, the computing unit 13 may determine, on the basis of the difference or frequency signal, whether there is an anomaly in the operation of the machine 8 and possibly on account of which component 14, 15, 16 the anomaly occurs.

Alternatively or additionally, the computing unit 13 may infer a degree of wear of the machine 8 and/or a respective degree of wear of one or more of the components 14, 15, 16 on the basis of the difference signal 22 or the frequency signal.

FIG. 3 schematically illustrates the described signals. FIG. 3 shows respective signal amplitudes of the operating signal 21, of an inverted reference signal 20 and of the difference signal 22 as a function of the time. The difference signal results as the sum of the signals 21, 20.

The improved concept specifies a possible way of analyzing the state of a machine and a method for generating a corresponding reference signal, which manages without large volumes of data and accordingly without high computing powers and nevertheless allows predictive planning of maintenance work in order to minimize downtimes or losses in quality in a manufacturing process by means of the machine.

The improved concept specifies, in particular, an acoustic method for the early detection of wear or anomalies in mechanical machine component parts, wherein a deviation between an operating noise of the machine recorded during the process using one or more microphones and an expected nominal noise is used as a measure of the state of wear or the presence of the anomaly. In this case, the nominal noise is predicted as the reference signal. The modeling of the reference signal or the generation of the reference signal can be considered, for example, to be an indication of a digital twin of the machine to be analyzed. The prediction of the noise development of the machine with the aid of the digital twin uses a deterministic idea of the nominal noise for different operating states of the machine, with the result that the correlation with different levels of wear already provides more reliable statements than conventional approaches and with a smaller data base.

LIST OF REFERENCE SIGNS

-   1 Method step -   2 Method step -   3 Method step -   4 Method step -   5 Method step -   6 Method step -   7 Method step -   8 Machine -   9 Analysis apparatus -   10 Microphone -   11 Microphone -   12 Microphone -   13 Computing unit -   14 Component -   15 Component -   16 Component -   17 Sensor apparatus -   18 Control unit -   19 Storage medium -   20 Inverse reference signal -   21 Operating signal -   22 Difference signal 

1. A method for generating at least one reference signal for an acoustic analysis of a state of a machine, the method comprising: providing at least one acoustic individual signal for each of at least two components of the machine; determining, by a computing unit, an expected acoustic overall signal based on the acoustic individual signals; and generating, by the computing unit, the at least one reference signal based on the expected acoustic overall signal.
 2. The method of claim 1, wherein a respective first individual signal of the acoustic individual signals is recorded for each of the at least two components while the respective component is in a corresponding first individual operating state, wherein a combination of the first individual operating states of the at least two components defines an operating state of the machine, and wherein determining the expected acoustic overall signal comprises determining, by the computing unit, the expected acoustic overall signal based on the first individual signals.
 3. The method of claim 1, wherein the expected acoustic overall signal is determined, by the computing unit, based on a pose of one of the at least two components, and wherein the pose is a combination of a position and an orientation of the respective component in three-dimensional space.
 4. The method of claim 1, wherein the expected acoustic overall signal is determined, by the computing unit, based on a nominal environmental condition of the machine.
 5. The method of claim 1, further comprising: determining, by a sensor apparatus, a current environmental condition of the machine; and determining, by the computing unit, the at least one reference signal based on the current environmental condition.
 6. A method for acoustic analysis of a state of a machine, the method comprising: recording an acoustic operating signal during operation of the machine; providing a reference signal, providing the reference signal comprising generating the reference signal, generating the reference signal comprising: providing at least one acoustic individual signal for each of at least two components of the machine; determining, by a computing unit, an expected acoustic overall signal based on the acoustic individual signals; and generating, by the computing unit, the reference signal based on the expected acoustic overall signal; and analyzing the state of the machine based on a deviation of the acoustic operating signal from the reference signal.
 7. The method of claim 6, further comprising: determining, by the computing unit, a current operating state of the machine; and providing the reference signal based on the current operating state.
 8. The method of claim 6, further comprising: generating, by the computing unit, a difference signal based on the deviation of the acoustic operating signal from the reference signal; and analyzing, by the computing unit, the state of the machine based on the difference signal.
 9. The method of claim 8, further comprising: generating, by the computing unit, a frequency signal based on the difference signal; and analyzing, by the computing unit, the state based on the frequency signal.
 10. The method of claim 6, further comprising: checking, by the computing unit, whether there is an anomaly in the operation of the machine based on the analysis of the state; determining, by the computing unit, a degree of wear of the machine based on the analysis of the state; or a combination thereof.
 11. An analysis apparatus for acoustic analysis of a state of a machine, the analysis apparatus comprising: at least one sound transducer; and a computing unit, wherein the at least one sound transducer is configured to generate respective acoustic individual signals based on respective individual operating noises of at least two components of the machine, wherein the computing unit is configured to determine an expected acoustic overall signal based on the individual signals, and wherein the computing unit is configured to generate a reference signal based on the expected acoustic overall signal.
 12. The analysis apparatus of claim 11, further comprising: a sensor apparatus configured to determine a current environmental condition of the machine, wherein the computing unit is configured to determine the expected acoustic overall signal based on the current environmental condition.
 13. The analysis apparatus of claim 11, wherein the at least one sound transducer is configured to generate an acoustic operating signal based on an operating noise of the machine, and wherein the computing unit is configured to analyze the state based on a deviation of the operating signal from the reference signal.
 14. (canceled)
 15. In a non-transitory computer-readable storage medium that stores instructions executable by one or more processors to generate at least one reference signal for an acoustic analysis of a state of a machine, the instructions comprising: providing at least one acoustic individual signal for each of at least two components of the machine; determining, by a computing unit, an expected acoustic overall signal based on the acoustic individual signals; and generating, by the computing unit, the at least one reference signal based on the expected acoustic overall signal. 